Nagorno-Karabakh ( nə-GOR-noh kar-ə-BAHK), also referred to as Artsakh by Armenians, is a landlocked region in the South Caucasus, within the mountainous range of Karabakh, lying between Lower Karabakh and Syunik, and covering the southeastern range of the Lesser Caucasus mountains. The region is mostly mountainous and forested.

Nagorno-Karabakh is a disputed territory, internationally recognized as part of Azerbaijan, but most of it is governed by the unrecognised Republic of Artsakh (also known as the Nagorno-Karabakh Republic (NKR)) since the first Nagorno-Karabakh War. Since the end of the war in 1994, representatives of the governments of Armenia and Azerbaijan have been holding peace talks mediated by the OSCE Minsk Group on the region's disputed status.

The region is usually equated with the administrative borders of the former Nagorno-Karabakh Autonomous Oblast, comprising 4,400 square kilometres (1,700 sq mi). The historical area of the region, however, encompasses approximately 8,223 square kilometres (3,175 sq mi).

On 27 September 2020, a new war erupted in Nagorno-Karabakh and the surrounding territories, which saw both the armed forces of Azerbaijan and Armenia report military and civilian casualties. Azerbaijan made significant gains during the war, regaining most of the occupied territories surrounding Nagorno-Karabakh and large parts of Nagorno-Karabakh, including the culturally significant city of Shusha. The war ended on 10 November 2020, when a trilateral ceasefire agreement was signed between Azerbaijan, Armenia and Russia, which forced Armenia to return all the remaining occupied territories surrounding Nagorno-Karabakh.